From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-oi0-f44.google.com (mail-oi0-f44.google.com [209.85.218.44]) by kanga.kvack.org (Postfix) with ESMTP id D88426B0253 for ; Mon, 10 Aug 2015 05:06:33 -0400 (EDT) Received: by oio137 with SMTP id 137so81828802oio.0 for ; Mon, 10 Aug 2015 02:06:33 -0700 (PDT) Received: from BLU004-OMC1S21.hotmail.com (blu004-omc1s21.hotmail.com. [65.55.116.32]) by mx.google.com with ESMTPS id xf6si13928508oeb.51.2015.08.10.02.06.32 for (version=TLSv1.2 cipher=ECDHE-RSA-AES128-SHA bits=128/128); Mon, 10 Aug 2015 02:06:32 -0700 (PDT) Message-ID: Subject: Re: [PATCH 2/2] mm/hwpoison: fix refcount of THP head page in no-injection case References: <1439188351-24292-1-git-send-email-wanpeng.li@hotmail.com> <20150810083529.GB21282@hori1.linux.bs1.fc.nec.co.jp> From: Wanpeng Li Date: Mon, 10 Aug 2015 17:06:25 +0800 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset="windows-1252"; format=flowed Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: Naoya Horiguchi Cc: Andrew Morton , "linux-mm@kvack.org" , "linux-kernel@vger.kernel.org" On 8/10/15 4:54 PM, Wanpeng Li wrote: > > > On 8/10/15 4:35 PM, Naoya Horiguchi wrote: >> On Mon, Aug 10, 2015 at 02:32:31PM +0800, Wanpeng Li wrote: >>> Hwpoison injection takes a refcount of target page and another refcount >>> of head page of THP if the target page is the tail page of a THP. >>> However, >>> current code doesn't release the refcount of head page if the THP is >>> not >>> supported to be injected wrt hwpoison filter. >>> >>> Fix it by reducing the refcount of head page if the target page is >>> the tail >>> page of a THP and it is not supported to be injected. >>> >>> Signed-off-by: Wanpeng Li >>> --- >>> mm/hwpoison-inject.c | 2 ++ >>> 1 files changed, 2 insertions(+), 0 deletions(-) >>> >>> diff --git a/mm/hwpoison-inject.c b/mm/hwpoison-inject.c >>> index 5015679..c343a45 100644 >>> --- a/mm/hwpoison-inject.c >>> +++ b/mm/hwpoison-inject.c >>> @@ -56,6 +56,8 @@ inject: >>> return memory_failure(pfn, 18, MF_COUNT_INCREASED); >>> put_out: >>> put_page(p); >>> + if (p != hpage) >>> + put_page(hpage); >> Yes, we need this when we inject to a thp tail page and "goto >> put_out" is >> called. But it seems that this code can be called also when injecting >> error >> to a hugetlb tail page and hwpoison_filter() returns non-zero, which >> is not >> expected. Unfortunately simply doing like below >> >> + if (!PageHuge(p) && p != hpage) >> + put_page(hpage); >> >> doesn't work, because exisiting put_page(p) can release refcount of >> hugetlb >> tail page, while get_hwpoison_page() takes refcount of hugetlb head >> page. >> >> So I feel that we need put_hwpoison_page() to properly release the >> refcount >> taken by memory error handlers. > > Good point. I think I will continue to do it and will post it out > soon. :) How about something like this: +void put_hwpoison_page(struct page *page) +{ + struct page *head = compound_head(page); + + if (PageHuge(head)) + goto put_out; + + if (PageTransHuge(head)) + if (page != head) + put_page(head); + +put_out: + put_page(page); + return; +} + Any comments are welcome, I can update the patch by myself. :) Regards, Wanpeng Li > > Regards, > Wanpeng Li > >> I'll post some patch(es) to address this problem this week. >> >> Thanks, >> Naoya Horiguchi > -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org